To address the question of whether the implementation of edge lines may have any negative safety effect on narrow rural two-lane highways with low traffic volume, a study was conducted to investigate the distribution of vehicles' lateral positions before and after the implementation of edge line markings. The data were collected at seven tangent and three curved sections on Louisiana rural two-lane highways where the pavement width is less than 22 ft and average daily traffic volume is between 86 and 1,855. The analysis results clearly show that after the implementation of edge lines, vehicles tended to move away from the pavement edge, which could lead to a reduction in run-off-road crashes--the most common type of crash on narrow two-lane highways. The analysis also shows that even though the counts of centerline crossings increased at several sites during the daytime, they did decrease at night, when the distribution of vehicles' lateral position is more centralized.
Abstract